Merge git://git.kernel.org/pub/scm/linux/kernel/git/bunk/trivial
[linux-2.6] / net / bridge / netfilter / ebt_among.c
1 /*
2  *  ebt_among
3  *
4  *      Authors:
5  *      Grzegorz Borowiak <grzes@gnu.univ.gda.pl>
6  *
7  *  August, 2003
8  *
9  */
10
11 #include <linux/netfilter_bridge/ebtables.h>
12 #include <linux/netfilter_bridge/ebt_among.h>
13 #include <linux/ip.h>
14 #include <linux/if_arp.h>
15 #include <linux/module.h>
16
17 static int ebt_mac_wormhash_contains(const struct ebt_mac_wormhash *wh,
18                                      const char *mac, __be32 ip)
19 {
20         /* You may be puzzled as to how this code works.
21          * Some tricks were used, refer to
22          *      include/linux/netfilter_bridge/ebt_among.h
23          * as there you can find a solution of this mystery.
24          */
25         const struct ebt_mac_wormhash_tuple *p;
26         int start, limit, i;
27         uint32_t cmp[2] = { 0, 0 };
28         int key = (const unsigned char) mac[5];
29
30         memcpy(((char *) cmp) + 2, mac, 6);
31         start = wh->table[key];
32         limit = wh->table[key + 1];
33         if (ip) {
34                 for (i = start; i < limit; i++) {
35                         p = &wh->pool[i];
36                         if (cmp[1] == p->cmp[1] && cmp[0] == p->cmp[0]) {
37                                 if (p->ip == 0 || p->ip == ip) {
38                                         return 1;
39                                 }
40                         }
41                 }
42         } else {
43                 for (i = start; i < limit; i++) {
44                         p = &wh->pool[i];
45                         if (cmp[1] == p->cmp[1] && cmp[0] == p->cmp[0]) {
46                                 if (p->ip == 0) {
47                                         return 1;
48                                 }
49                         }
50                 }
51         }
52         return 0;
53 }
54
55 static int ebt_mac_wormhash_check_integrity(const struct ebt_mac_wormhash
56                                             *wh)
57 {
58         int i;
59
60         for (i = 0; i < 256; i++) {
61                 if (wh->table[i] > wh->table[i + 1])
62                         return -0x100 - i;
63                 if (wh->table[i] < 0)
64                         return -0x200 - i;
65                 if (wh->table[i] > wh->poolsize)
66                         return -0x300 - i;
67         }
68         if (wh->table[256] > wh->poolsize)
69                 return -0xc00;
70         return 0;
71 }
72
73 static int get_ip_dst(const struct sk_buff *skb, __be32 *addr)
74 {
75         if (eth_hdr(skb)->h_proto == htons(ETH_P_IP)) {
76                 struct iphdr _iph, *ih;
77
78                 ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
79                 if (ih == NULL)
80                         return -1;
81                 *addr = ih->daddr;
82         } else if (eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) {
83                 struct arphdr _arph, *ah;
84                 __be32 buf, *bp;
85
86                 ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
87                 if (ah == NULL ||
88                     ah->ar_pln != sizeof(__be32) ||
89                     ah->ar_hln != ETH_ALEN)
90                         return -1;
91                 bp = skb_header_pointer(skb, sizeof(struct arphdr) +
92                                         2 * ETH_ALEN + sizeof(__be32),
93                                         sizeof(__be32), &buf);
94                 if (bp == NULL)
95                         return -1;
96                 *addr = *bp;
97         }
98         return 0;
99 }
100
101 static int get_ip_src(const struct sk_buff *skb, __be32 *addr)
102 {
103         if (eth_hdr(skb)->h_proto == htons(ETH_P_IP)) {
104                 struct iphdr _iph, *ih;
105
106                 ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
107                 if (ih == NULL)
108                         return -1;
109                 *addr = ih->saddr;
110         } else if (eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) {
111                 struct arphdr _arph, *ah;
112                 __be32 buf, *bp;
113
114                 ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
115                 if (ah == NULL ||
116                     ah->ar_pln != sizeof(__be32) ||
117                     ah->ar_hln != ETH_ALEN)
118                         return -1;
119                 bp = skb_header_pointer(skb, sizeof(struct arphdr) +
120                                         ETH_ALEN, sizeof(__be32), &buf);
121                 if (bp == NULL)
122                         return -1;
123                 *addr = *bp;
124         }
125         return 0;
126 }
127
128 static int ebt_filter_among(const struct sk_buff *skb,
129                             const struct net_device *in,
130                             const struct net_device *out, const void *data,
131                             unsigned int datalen)
132 {
133         struct ebt_among_info *info = (struct ebt_among_info *) data;
134         const char *dmac, *smac;
135         const struct ebt_mac_wormhash *wh_dst, *wh_src;
136         __be32 dip = 0, sip = 0;
137
138         wh_dst = ebt_among_wh_dst(info);
139         wh_src = ebt_among_wh_src(info);
140
141         if (wh_src) {
142                 smac = eth_hdr(skb)->h_source;
143                 if (get_ip_src(skb, &sip))
144                         return EBT_NOMATCH;
145                 if (!(info->bitmask & EBT_AMONG_SRC_NEG)) {
146                         /* we match only if it contains */
147                         if (!ebt_mac_wormhash_contains(wh_src, smac, sip))
148                                 return EBT_NOMATCH;
149                 } else {
150                         /* we match only if it DOES NOT contain */
151                         if (ebt_mac_wormhash_contains(wh_src, smac, sip))
152                                 return EBT_NOMATCH;
153                 }
154         }
155
156         if (wh_dst) {
157                 dmac = eth_hdr(skb)->h_dest;
158                 if (get_ip_dst(skb, &dip))
159                         return EBT_NOMATCH;
160                 if (!(info->bitmask & EBT_AMONG_DST_NEG)) {
161                         /* we match only if it contains */
162                         if (!ebt_mac_wormhash_contains(wh_dst, dmac, dip))
163                                 return EBT_NOMATCH;
164                 } else {
165                         /* we match only if it DOES NOT contain */
166                         if (ebt_mac_wormhash_contains(wh_dst, dmac, dip))
167                                 return EBT_NOMATCH;
168                 }
169         }
170
171         return EBT_MATCH;
172 }
173
174 static int ebt_among_check(const char *tablename, unsigned int hookmask,
175                            const struct ebt_entry *e, void *data,
176                            unsigned int datalen)
177 {
178         struct ebt_among_info *info = (struct ebt_among_info *) data;
179         int expected_length = sizeof(struct ebt_among_info);
180         const struct ebt_mac_wormhash *wh_dst, *wh_src;
181         int err;
182
183         wh_dst = ebt_among_wh_dst(info);
184         wh_src = ebt_among_wh_src(info);
185         expected_length += ebt_mac_wormhash_size(wh_dst);
186         expected_length += ebt_mac_wormhash_size(wh_src);
187
188         if (datalen != EBT_ALIGN(expected_length)) {
189                 printk(KERN_WARNING
190                        "ebtables: among: wrong size: %d"
191                        "against expected %d, rounded to %Zd\n",
192                        datalen, expected_length,
193                        EBT_ALIGN(expected_length));
194                 return -EINVAL;
195         }
196         if (wh_dst && (err = ebt_mac_wormhash_check_integrity(wh_dst))) {
197                 printk(KERN_WARNING
198                        "ebtables: among: dst integrity fail: %x\n", -err);
199                 return -EINVAL;
200         }
201         if (wh_src && (err = ebt_mac_wormhash_check_integrity(wh_src))) {
202                 printk(KERN_WARNING
203                        "ebtables: among: src integrity fail: %x\n", -err);
204                 return -EINVAL;
205         }
206         return 0;
207 }
208
209 static struct ebt_match filter_among = {
210         .name           = EBT_AMONG_MATCH,
211         .match          = ebt_filter_among,
212         .check          = ebt_among_check,
213         .me             = THIS_MODULE,
214 };
215
216 static int __init ebt_among_init(void)
217 {
218         return ebt_register_match(&filter_among);
219 }
220
221 static void __exit ebt_among_fini(void)
222 {
223         ebt_unregister_match(&filter_among);
224 }
225
226 module_init(ebt_among_init);
227 module_exit(ebt_among_fini);
228 MODULE_LICENSE("GPL");